CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating revenues
Electric	$ 749,461	$ 734,264
Natural gas	373,203	456,337
Steam and other	12,786	12,942
Total operating revenues	1,135,450	1,203,543
Operating expenses
Electric fuel and purchased power	322,758	334,470
Cost of natural gas sold and transported	228,744	309,805
Cost of sales — steam and other	5,693	4,978
Operating and maintenance expenses	182,417	175,524
Demand side management program expenses	30,069	35,195
Depreciation and amortization	100,043	93,316
Taxes (other than income taxes)	50,326	41,818
Total operating expenses	920,050	995,106
Operating income	215,400	208,437
Other income, net	687	797
Allowance for funds used during construction — equity	2,806	11,430
Interest charges and financing costs
Interest charges — includes other financing costs of $1,505 and $1,720, respectively	43,090	43,972
Allowance for funds used during construction — debt	(1,098)	(4,208)
Total interest charges and financing costs	41,992	39,764
Income before income taxes	176,901	180,900
Income taxes	65,935	62,497
Net income	$ 110,966	$ 118,403